Spark plug manufacture



Aus- 10, 1948. D. H. CORBIN 2,446,908

SPARK PLUG MANUFACTURE Aug. 10, 1948. D. H. coRBlN 2,445,908

SPARK PLUG MANUFACTURE Filed Nov. l. 1943 6 Sheets-Sheet 2 In venlor 'i \yfy, w#-

` I 9(- Ailomeys D. H. CORBIN SPARK PLUG MANUFACTURE Aug. 1Q, 1948.

6 Sheets-Sheet 3 Filed Nov. l, 1943 Aug. 10, 1948. D. H. coRBlN SPARK PLUG MANUFACTURE l 6 Sheets-Sheet 4 4Filed Nov. 1, 194:',

Au@ 10, 1948. D. H. CORBIN 2,446,908

SPARK PLUG MANUFACTURE Filed Nov. l, 1943 6 Sheets-Sheet 5 F IG. 9.

//85 a; o 0,/ 7*@ O I l l\ l y i l' E E! O\\ IO O l e :0 99 r z E :c :e Le :e Si E Inventor @ngy/rz/z By fZ/ wy Attorneys AU@ 10, 1943- D. H. coRBlN 2,446,908

SPARK PLUG MANUFACTURE Filed Nov. l, 1943 6 Sheets- Sheet 6 Patentedv Aug. 10, 1948 SPARK PLUG MANUFACTURE Douglas Haynes Corbin, Dunstable, England, as-

signor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application November 1, 1943, Serial No. 508,549 In Great Britain November 6, 1942 icwm. l

This invention relates to the manufacture of spark plugs for internal combustion engines.

In general such spark plugs are of various con'- structions; and furthermore the form of and manner of forming the central electrode within the insulator vary considerably according to the requirements that have to be fulfilled.

One form of central electrode, with which the present invention is concerned, has the lower part consisting of a metallic core moulded in position in the bore of the insulator. One manner of forming such an electrode part is by heating and pressing a mass of metal in the insulator bore, such that by plastic deformation it is moulded to the bore. The metal can be of powdered or solid form. Another manner of forming such an electrode Vpart is by heating a mass of metal to a molten condition within the insulator bore, so that it will mould itself to the bore.

The metals of greatest utility in such methods are silver and copper, with silver the preferred. Their heat, electrical and physical properties render them the most suitable known at the present time.

The object of the present invention is to improve the manufacture of spark plugs by moulding part of the central electrode in the insulator bore under centrifugal pressure.

This is eiIected by subjecting the insulator assembly to rotation about a centre on the insulator axis, with the metallic mass in at least a plastic but `preferaizvly in a molten condition. By effecting the rotation whilst the metal is molten the need for any weight to compress the metal in a powdered or plastic condition is avoided. Whilst the insulator is rotating it is cooled and thus the metal sets whilst it is held compressed against the inner wall of the insulator. The cooling, however, can be effected after rotation.

In carrying out this improved process in a preferred manner, an insulator of dense refractory oxide or oxides has a small spark tip of platinum or like metal positioned at the lower end of its bore. 'I'he tip is prevented from dropping out by having its head enlarged or distorted with respect to the lower end of the bore. A small stick oi' silver is then inserted on the top of the tip. The whole assembly is then heated at least up to the melting point of silver, and then while the silver is molten, the whole assembly is rapidly rotated about a centre above the top of the insulator, with the tip outward. The rotation is continued until the silver is solidiiled. When suiiiciently cool, the remainder of the insulator assembly and of the whole plug assembly are completed in the usual way.

Apparatus for carrying out the process aforesaid can take various forms, and a convenient construction of machine for the said purpose will now be described with particular reference to the accomanying sheets of drawings.

In the drawings:

Figure 1 is a side elevational view of the machine taken along the line l--I of Figure 3;

Figure 2 is a fragmentary view in plan of the upper portion of the machine illustrated in Figure 1;

Figure 3 is a. fragmentary View of the machine inplan section taken along the line 3-3 of Figure 1;

Figure 4 is a detail view mainly in plan of part of the driving mechanism;

Figure 5 is an expanded fragmentary view in side elevation of the compressed air valve control mechanism utilized in Figure l;

Figure 6 is a cross sectional view illustrating the indexing cam employed in the machine;

Figure 7 is a developed view of the indexing cam illustrated in Figure 6;

Figure 8 is a detail view in front elevation of a holder for an insulator during its treatment in the machine showing also the method of suspending the said holder in the machine;

Figure 9 is a detail view in vertical section of a compressed air cylinder for raising the hoods utilised in the machine illustrated; and

Figure 10 is a diagrammatic representation of the compres-sed air lay-out as incorporated in the aforesaid machine.

In the drawings like numerals ci reference indicate similar parts in the several views.

As illustrated in the drawings, the machine incorporates an upper triangulated frame member l5 and a lower triangulated frame member I6 which are interconnected by uprights il, said uprights l1 being supported at their lower ends upon feet i8. Slidably mounted within bearings Situated at the hubs of the frame members Arods 21.

The hydraulic cylinder has valve controlled communication with a vessel 28 containing oil. The cover plate 29 for the said oil vessel 28 is provided with an'aperture which is in communication with a pipe line 38 associated with a compressed air control valve 3| to be referred to hereinafter.

Fixed to the lifting rod 28 intermediate the frame members I5 and I6 is a six armed spider 32. The outer end of each arm of the spider 32 is forked and the limbs of each forked portion are furnished with bearings for a vertically disposed spindle 33. The portion of a spindle 83 intermediate the limbs of a forked portion has '.Ixed thereto an elongated pulley 34 and the lower ends of each of the said spindles 33 support a carrier disc 35 from which is pivotally suspended a plurality of wire holders 36 for the insulators 31 (see also Figure 8). As shown, each carrier disc 35 is adapted to accommodate eighteen insulator holders 36. Slidably mounted on a downward extension 32| of each arm of the spider 32 is an annular hood 38 the internal diameter of which slightly exceeds the sum of the diameter of a carrier disc 35 and the length of the insulator holders 36.

It should be noted that when suspended from a carrier disc 35 the holders 36 are caused to hang as shown in Figure 8 with one limb in contact with an adjacent edge of the carrier disc 35 for a purpose to be described hereinafter.

The elongated pulleys 34 when in certain positions cooperate with a pair of endless driving belts 39 and 48, the belt 39 hereinafter being termed the slow speed belt 39 and the belt 48 the fast speed belt 48. The slow speed belt 39 passes around a pulley 4| secured on the lower end of a sleeve 42 rotatably mounted in bearings in a guide I5| carried by the frame member I5 and a pulley 43 carried at one end of an arm 44 which is pivoted to a bracket 45 clamped to an upright |1, a spring 46 anchored to the arm 44 and bracket 45 serving to tension the said slow speed belt 39. At its upper end the sleeve 42 carries a pulley 41 which is adapted to be driven Iby an endless belt 48 from a pulley 49 fixed to a spindle 58 to which is pinned a wormwheel 5-I which is adapted to be driven by Y an electric motor 52 through the medium of a worm 53 secured to the driving shaft 52| of the said motor 52. The electric motor 52 is mounted on the upper side of a platform 54 bolted to two of the arms of the frame member I5.

The fast speed belt 48 passes around a pulley 55 fixed to the lower end of a spindle 56 which is rotatably mounted in the sleeve 42 and a pulley 51 carried by an arm of a lever 58 fulcruimed on a bracket 59 clamped to an upright I1, the lever 58 and bracket 59 being anchored to the ends of a spring 68 which tends constantly to tension the high speed belt 48. Fixed to the upper end of the spindle 56 is a pulley 6I which is adapted to be driven by an endless belt 62 4 from a pulley 63 xed to the end of the motor driving shaft 52|.

The spindle 58 has secured thereto also a pulley 64 which is adapted to drive by endless belt 65 a pulley 66 fixed to the end of a vertical shaft 61 mounted in bearings formed in a pedestal 68 carried by a platform 69 supported by means of upstanding rods 18 from the frame member I5. This said shaft 61 carries a worm 12 which meshes with a wormwheel 13 fixed on one end of a horizontally disposed shaft 14. The other end of the horizontal shaft 14 carries a cam disc 15.

Adapted to abut the cam face of the cam disc 15 is a roller- 168 located at one end of a plunger 16 which is slidably mounted in brackets supported from the platform 69. A spring 18 tends to maintain abutment between the roller 168 and the presented cam face. The other end of the plunger 16 is formed with a shoulder 16| which cooperates with the free end of a.v gravity operated catch link 19. This link 19 is pivoted to one end of a second slidable plunger 88 which in turn is associated with the piston rod 3II of the air control valve 3|. The piston rod 3| I, plunger 88, link 19 and plunger 18are arranged axially and a spring 8| tends to move the plunger 88 towards the cam disc 15.

Disposed below the central portion of the link 18 is the head of a tappet 82 the lower end of which is located above the upper end of the liftlng rod 28.

The spider 32 is provided with a pair of oppositely disposed axles 83 having mounted thereon rollers 84 said rollers 84 engaging within the grooves 85 of an indexing cam 86 associated with the underside of the hub of the frame member I5.

The plane containing upper surface of the frame member I6 is laid out with six equidistantly spaced stations marked-A, B, C, D, E, F.

The station A is termed the idle station, the station .B the pre-heating station, the station C the inal heating station, the station D the centrifuging station, the station E the cooling station and the station F the unloading and loading station.

The stations F and A are presented to the operator who effects the loading and unloading by hand and controls the machine by means of a push button control 81 for the electric motor 52 and a three-way valve 88 for the compressed air control, see Fig. 3, from a table 99 supported by two of the arms of the frame member I6. The pre-heating and final heating are effected by electric furnaces *89, 98 mounted on a platform supported by two other arms of the frame member I6. The said furnaces 89, 98 are annular and generally similar in construction and each embodies an electrically heated annular chamber 9| which is situated and dimensioned so that the insulators 31 can depend thereinto when a loaded carrier disc 35 is located at the stations B or C, see Fig. 1.

During the time when a carrier disc 35 is at stations B or C the respective elongated pulleys 34 are in engagement with the adjacent length of the slow speed belt 39 so that the carrier discs 35 are rotated slowly whilst at the said station. Meanwhile the elongated pulley 34 of the carrier disc 35 which is located at the centrifuging station D is in engagement with the fast speed belt 48 whereby the insulators 31 concerned are rotated rapidly and swung out by centrifugal force into a substantially horizontal position. At stations F and A the table 99 supports six pneumatic cylinders 62 which are symmetrically arranged at each station so that jawed portions 63 at the upper ends of the piston rods 94 are located below the rims of the hoods 36 when disposed at the said stations F and A. The supply of compressed air to the cylinders 62 is controlled by the threeway valve -86 already referred to in conjunction with a valve 35 and distributor 96, see Fig. 10.

Adjacent to the operator is located a screw down valve 91 for cutting off communication between the hydraulic cylinder` 25 and the oil vessel 28 when required, see Fig. 1.

The operation of the machine is as follows:

At the loading station Fthe holders 36 are filled with insulators 31 in the central holes in which have been inserted the lengths of silver rod which are to constitute the metallic cores of the central electrodes.

When the loading operation is complete the motor 52 is put into action and after a predetermined period of time the lifting rod and parts fixed thereto are raised so that the carrier disc 35 is indexed one step to station A and lowered in a manner determined by the movement of the rollers 84 in the grooves 85 of the indexing cam 66. The succeeding carrier disc 35 which arrives at station F is then unloaded if the machine has been previously in operation and the cooled insulators 31 removed and new insulators 31 and their fillings inserted. In due course the carrier disc 35 from station A is indexed a further stage whereby the said carrier disc 35 is brought to station B at which is located preheating furnace 66. In a like manner the carrier discs 35 are passed progressively to each station where they remain for a definite and constant period of time.

When a carrier disc 35 is correctly located at station B or C the lowering movement locates the insulators within the respcetive annular furnace chambers 6| with the furnaces partially enveloped by the hoods 38 as seen in Fig. 1. As stated hereinbefore the insulators 31 when at station B are preheated and acquire a final heating when indexed to station C, the division of the heating into two parts reducing the time at which a carrier disc 35 would otherwise be required to remain at a single heating station. The nal heating melts the silver rods so that when station D is reached where the carrier discs 35 are r0- tated at high speed the insulators 31 are swung into a horizontal position under the inuence of centrifugal force whereby the molten silver in the central bores of the respective insulators 31 is caused to accommodate itself under centrifugal force to the bore of the said insulators 31 and in so doing to expel air and other trapped gases from the bore of the insulators 31, and from the mass of molten silver.

After centrifuging, indexing to station E obtains where cooling takes place with the insulators 31 at rest and ultimately progress is made to station F where unloading and loading is carried out.

When at stations F and A the hoods 38 are lifted by the jawed portions 93 of the piston rods $4 of the pneumatic cylinders 92 by admitting compressed air to the said cylinders 92.

The control of the air valve 3l is determined as follows. During periods between stations the plunger 16, link 16 and plunger 80 are rigid so that when a peak of the cam disc 15 traverses the roller 160 an axial thrust is exerted whereby the valve 3| is operated to cause; compressed air to flow into the oil vessel 26. The oil displaced by the air passes into the hydraulic cylinder and raises the lifting rod 26 and thus causes the rollers 84 to traverse the grooves of the cam 66. As the lifting rod 20 approaches the top of its stroke the upper end of the said rod strikes the tappet 82 which in turn lifts the catch and frees the link 18 thus permitting the spring 8i to move the plunger so that the valve 3l is caused to cut off the supply of compressed air to the oil vessel 26. Consequently the lifting rod 26 falls under the influence of gravity and indexing takes place by virtue of the movement of the rollers 64 in the cam grooves 85. The lowering of the lifting rod 20 in conjunction with the movement of the cam disc 15 permits the catch link 13 to fall and reseat itself on the shoulder 16I of the plunger 16.

In an emergency the motor 52 can be stopped and the three-way valve 66 manipulated to cause the lifting rod 20 to be raised likewise the hoods 36 at stations F and A, the said rod 20 being maintained in a raised position by retaining a head in the hydraulic cylinder 25 by manipulating the valve control 31 to shut off communication between the said hydraulic cyliner 25 and the oil vessel 26.

By causing the holders 36 to hang as shown in Figure 10 it is found that the friction engendered by one limb of the holder contacting an edge of the carrier disc 35 exerts a restraint on the swinging movement permitted to the holders so that insertion in and removal from the heating chambers 9| is facilitated.

A machine constructed as hereinbefore described admits of an improved process being carried out continuously and substantially automatically.

Molten is used in the following claim to designate a condition of the electrode material which permits it to flow or be deformed by the action of centrifugal force as disclosed herein.

I claim:

A machine for use in the manufacture of spark plugs embodying a frame structure, a rotatable and vertically displaceable lifting member mounted on said frame structure adapted to be moved step by step from station to station, a plurality of shafts rotatably supported by said lifting member, carrier members flxedly attached to each of said shafts for rotation therewith, means for pivotally suspending from the carrier members a plurality of insulators the bores of which have been already loaded with the metal required to form the core of the central electrode, said means permitting the insulators to swing outwardly under centrifugal force with the spark tip ends of the insulators directed outwardly, a pair of furnaces located at successive stations for heating the loaded insulators so that the metal becomes plastic or molten, means for slowly rotating the carriers while at said stations to produce even heating, means at a succeeding station for imparting a fast rotation to the carrier so that the loaded insulators are subjected to centrifugal force and the plastic or molten metal caused to fill the spaces to be occupied by the metallic core of a central electrode, and so that air and any trapped gases are expelled, cooling and unloading stations, means for intermittently moving said lifting member from station to station comprising an indexing cam, means associated with the lifting member and which cooperates with the indexing cam for effecting an indexing of the said lifting member and the carrier means supported thereby as determined by a raising and lowering of the aforesaid lifting member, a hydraulic means for effecting the raising of the said lifting 7 member, pneumatic means for controlling th actuation of said hydraulic mechanism, and trip mechanism for governing the operation of the pneumatic means according to a. prescribed time cycle.

DOUGLAS HAYNES CORBIN.

REFERENCES CITED Name Date Sebenius Jan. 6, 1891 Number Number 8 Name Date Heath May 18, 1920 Reichold July 5, 1927 Wishart Nov. 6, 1928 Morgan Sept. 19, 1933 May June 26, 1934 Adams Dec. 3, 1935 Corbin June 13, 1939 Esnault-Pelterie Oct. 1, 1940 Aderer Feb. 25, 1941 McCarroll et al. A Jan. 20, 1942 Batie Feb. 17, 1942 Batie Aug. 11, 1942 Anderson Dec. 8, 1942 

